I've read that if photovolaics were mass-produced on a national scale that they are highly likely to deplete precious metal reserves such as silver, and others. I like photovoltaics, and they will pay for themselves over a period of 20 years or so, but the outlay is large.

If you really want an efficient, environmentally friendly solar power, grow a field of sugar cane, corn, or some other high-starch, high-cellulose crop. The biomass will convert between 17 - 30 percent of solar energy into plant fibers. These in turn can be converted into ethanol, a combustable fuel that can run a generator, a turbine, or a fuel cell. Producing ethanol is done with a 25% energy surplus (4.5 - 7.5 percent net efficiency), and most IC engines are around 20% efficient - fuel cells are up to 40 percent efficient or higher. Photovoltaics are often slightly more efficient, but efficiency isn't everything. Try ponying up the cash to cover 10,000 acres with solar panels.... hey buddy how 'bout a loan. ;-)

The most significant aspect is that biomass is good for the environment - the more the better. And with ethanol you get a storable, portable fuel, that can be use for just about anything, in far greater quantities and a fraction of the cost of photovoltaics.